Data from 372 studies involving over 99,000 patients were analysed by Dr Marc Stone from the US Food and Drug Administration and colleagues.

They found that antidepressants were protective against suicidal thinking and behaviour for over-65s and moderately protective for those aged 25-64, but that adults aged under 25 taking antidepressants were at increased risk.

Dr Stone and his team said the age-dependent increase in suicidal thinking could be approached like any other uncommon but serious adverse effect.

'Patients whose illnesses pose less risk of suicidal ideation or behaviour could have less potential to benefit from any effect drug treatment might have on reducing suicidal sequelae, but be little different from patients with major depression in vulnerability to adverse effects,' they said.